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Premature thelarche in an infant girl with failure to thrive related to dietary soy exposure
  1. Serena Su Ying Chang,
  2. Nandhakumar Nagarajan and
  3. Joanne Mui Ching Tan
  1. Department of Paediatric Medicine, KK Women's and Children's Hospital, Singapore
  1. Correspondence to Dr Serena Su Ying Chang; serena.chang.s.y{at}


A 7-month-old female infant presented with failure to thrive. She was breastfed till 3 months of age, thereafter switched to soy-based milk formula. There was no history to suggest excess energy losses, recurrent infections or chronic diarrhoea. Three months after switching to exclusive soy-based milk formula, parents noticed significant enlargement of both breasts. Clinical examination was unremarkable except for enlargement of both breasts. None of the other secondary sexual characteristics were present. Initial blood investigations showed hyponatraemic hypokalaemic hypochloraemic metabolic alkalosis, which corrected after 2 days with intravenous hydration. The patient subsequently maintained normal electrolyte balance with recommended intake of cow’s milk-based standard formula milk.

Further exploration of her soy-based milk revealed that it was low in sodium and calories, unsuitable for children. This was not a standard and approved infant soy-based formula milk. She achieved excellent weight gain and reduction of breast size on cessation of soy-based milk formula.

  • malnutrition
  • childhood nutrition (paediatrics)
  • failure to thrive
  • infant nutrition (including breastfeeding)

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  • Contributors SSYC: Writing original draft. JMCT, NN and SSYC: Writing, reviewing and editing. SSYC, JMCT and NN: Approval of final manuscript.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Patient consent for publication Parental/guardian consent obtained.

  • Provenance and peer review Not commissioned; externally peer-reviewed.